Notwithstanding the IRC techniques discussed above, there continues to exist a need in the art for improved interference reduction receivers, methods, and related terminals and accessories.
It is, therefore, an object of the present invention to provide improved radio communications methods and receivers.
It is another object of the present invention to reduce interference after demodulation in radio communications methods and receivers.
The present invention provides receivers and methods that allow a reduction in interference by combining soft symbols. In particular, transmitted data signals are received over a plurality of paths and the received data signals may include interference components. The received data signals are processed to provide a plurality of soft symbols that correspond to the transmitted data signal. The plurality of soft symbols are combined to reduce the interference component of the received data signal and provide an output signal that corresponds to the transmitted data signal. Accordingly, equalizers that provide soft symbols may be used with combiners to reduce interference, thereby reducing the need to create custom devices to reduce interference. In contrast, conventional systems may be custom-designed to process the received data signal to reduce interference and may thereby increase the cost of the system.
Each equalizer may reduce the interference of at least two interfering portions of the received data signal. Each equalizer may be a coherent detector that reduces interference of at least two interfering portions of the received data signal by estimating channel coefficients and applying the estimated channel coefficients to the at least two interfering portions of the received data signal. Accordingly, equalizers may be used to provide soft symbols for each of the respective received data signals to allow a reduction in the cost of the system.
The combiner combines the plurality of soft symbols based on estimated parameters to provide a combined soft symbol and the combined soft symbol is detected to provide a hard value. The combined soft symbol may be used to generate the estimated parameters. According to the present invention, combiners may be used in conjunction with the equalizers described herein to reduce interference.
In particular, the combiner can include an adaptive combiner that generates weighted soft symbols based on a plurality of soft symbols and sums the weighted soft symbols to provide a combined soft symbol. In addition, a detector can detect the combined soft symbol to provide a hard value, wherein the hard value is an estimated value of the transmitted data signal based on the combined soft symbol. A comparator can compare the hard value to the combined soft symbol to provide the error signal that indicates the difference between the combined soft symbol and hard value.
In another aspect of the present invention, the transmitted data signal can be a predetermined synchronization signal, wherein the predetermined synchronization signal corresponds to a known combined soft symbol, and the combiner can modify the estimated parameters based on the known combined soft symbol. The present invention, therefore allows for the reduction of interference without requiring an error signal as described above.
In another aspect of the present invention, a receiver such as a mobile user terminal may be combined with an accessory that includes an external antenna. The external antenna provides a received data signal to the mobile user terminal. The addition of the external antenna may therefore be used to reduce interference. The mobile user terminal includes a housing wherein the equalizers and the combiner are located within the housing. An antenna is attached to the housing and coupled to a first one of the equalizers located in the housing. A port located on the housing is coupled to a second one of the equalizers. The port provides a detachable coupling between the second equalizer and the external antenna.
Alternately, the accessory may include an equalizer that receives a received data signal from the external antenna. In particular, the external antenna is separate from the mobile user terminal and receives the received data signal corresponding to the transmitted data signal from the remote source including an interference component. The accessory equalizer is separate from the mobile user terminal and processes the received data signal from the external antenna to provide an accessory soft symbol. The accessory soft symbol is provided to the mobile user terminal via an accessory connector. The accessory connector connects to the port on the mobile user terminal wherein the accessory soft symbol is provided to the combiner in the mobile user terminal.
In still another aspect of the present invention, the received data signal may be converted to a digital signal. In particular the received data signal can be converted to baseband digital samples and processed to provide the plurality of soft symbols.